Synthetic plastic rope for automatic devices



Dec. 10, 1968 R. 1.. STANTON 3, 5, 52

SYNTHETIC PLASTIC ROPE FOR AUTOMATIC DEVICES Filed April 12, 1966 I NVEN TOR. AOdf/Qf 4. rr4/vra/v United States Patent 3,415,052 SYNTHETIC PLASTIC ROPE FOR AUTOMATIC DEVICES Robert L. Stanton, Maplewood, N.J., assignor to American Manufacturing Company, Inc., Brooklyn, N.Y., a corporation of Delaware Filed Apr. 12, 1966, Ser. No. 542,007 7 Claims. (Cl. 57-144) ABSTRACT OF THE DISCLOSURE This rope contains six outer strands twisted around a central core, this central core comprising a plurality of twisted yarns of nylon. The outer layer of each of the six outer strands comprises alternating yarns of plied nylon and plied polypropylene. The inner core of each of these outer strands is comprised of substantially untwisted continuous filaments of nylon.

This invention relates to cordage and in particular to a synthetic plastic rope particularly intended for use with automatic reeling and unreeling devices such as automatic winches.

At one time all ships were tied to the pier manually by members of the ships crew. In recent years due to the use of much larger vessels, higher labor costs and a desire to eliminate safety hazards, automatic winching machines are increasingly used. They have come into widespread use, for example, on large capacity vessels such as tankers. These winches pay out or reel in wire mooring lines.

Conventional non-wire mooring ropes intended for manual handling are not suitable for use with the winching machines since they are too soft and too easily deformable when wound onto the winch. If wound in multiple layers, they would be too easily flattened and worn out by the pressure of one layer on the other. Consequently, Wire ropes have been customarily used with these machines. Wire mooring lines are generally quite expensive.

Wire mooring lines are subject to heavy corrosion effects, especially in salt water. Furthermore, wire lines have somewhat limited flexing life and can damage socalled fair leads and chocks in use. Wire lines are also characterized by a limited capability of resisting sudden shocks. Futhermore, their limited ability to absorb such shocks tends to transmit the shock to the winch itself with possible resultant wear or damage thereto. Wire lines are also considerably heavier per linear foot than non-wire types of cordage and therefore more men are needed to handle them. They usually have a considerably higher twist than non-wire ropes.

Wire lines also have the disadvantage that if they become fouled in the propeller of a ship, they can cause substantial damage. Furthermore, considerable effort and expense is usually required to disentangle them. Moreover, over a period of time, so-called fish hooks, i.e. splintered and curved fragments of the individual wires develop on the outer surface of the wire rope. This presents a safety hazard to all personnel handling the rope.

It is, therefore, among the objects of the present invention to provide a rope having the following features:

(1) superior corrosion resistance,

(2) less expensive,

(3) greater shock-absorbing ability than wire ropes, (4) less damaging to fair leads and chocks,

(5) less damaging to the automatic winching equipment,

(6) less potential damage to the ships propeller and greater ease in unfouling it,

(7) fewer maintenance problems,

(9) lighter in weight, (10) longer flexing life.

Other objects of the invention will doubtless appear to one skilled in the art upon perusal of the drawings and specification herein.

In accordance with the invention there is provided a synthetic plastic rope having a central core comprised of a plurality of yarns of a readily extensible plastic material having a high tensile strength. This core lies substantially along the longitudinal axis of the rope. Around it are disposed a plurality of strands of plastic materials. A selected number (which may be all) of the strands include an outer layer which contains a high tensile strength, high melting point plastic material, such as nylon, as well as a lower melting point plastic material, such as polypropylene. This outer layer surrounds a core of substantially untwisted, continuous filament yarns of a high tensile strength plastic such as nylon.

In one highly satisfactory form of the invention, there were six outer strands twisted around a central core. The outer layer of each of the outer strands comprised alternating yarns of plied nylon and plied polypropylene. These yarns surrounded a core of substantially untwisted continuous filaments of nylon. The central core of the rope comprised a plurality of twisted 3-ply yarns of nylon.

FIGURE 1 is a side elevation view, partly in phantom, of the novel, non-wire rope constructed according to one form of this invention.

FIGURE 2 is an enlarged cross-sectional view of the rope, partly in phantom, shown in FIG. 1.

Referring to FIGURES 1 and 2, there is shown a rope generally indicated at the numeral 5 consisting of six outer strands indicated at the numerals 6 7, 8, 9*, 10, and 11. These strands are twisted (Z-twist) around a central core which is disposed substantially along the longitudinal axis of the rope.

The core 15 is primarily comprised of a plurality of twisted yarns of a highly extensible and strong plastic material such as nylon. For example, as shown it may consist of a plurality of 3-ply yarns (Z-twist) each made from twisted singles yarns (S-twist). The 3-ply yarns are laid into a strand having an S-twist ratio within the range of about 3 to 4. Throughout this specification, the twist ratios given are obtained by dividing the helical length of a single turn by the diameter of the compression tube or die used to form the strand, rope, yarn, etc. as the case may be. during fabrication.

Disposed around the core 15 are the six strands 6-11 which can be substantially similar to one another. By having a higher number of outside strands than in conventional marine non-wire ropes, a more circular cross-section is obtained. This means that there will be shallower valleys between adjacent outer strands and thus there will be less abrasion. In the illustrated form of the invention, all of the strands have a plurality of Z-twisted 3-ply outer yarns 20. Each of the three yarns a, 20b, 200 in the 3- ply yarn is comprised of low-twist (S-twist) polypropylene monoifilarrents 19. As shown these polypropylene yarns 20 are alternated with a plurality of 3-plly Z-twisted nylon yarns 21 each consisting of yarns 21a, 21b, and 210 made of nylon multi-filaments having an S-twist. These outer yarns 20 and 21 may be laid with a twist ratio in the range 3.5 to 4.5, a typical ratio being 4.2. These nylon yarns 21 constitute a large portion of the outer surface of the entire rope 5 which is wound around or bears on various frictional surfaces. As nylon has a considerably higher melting point than polypropylene, it is able to resist the greater pressures and temperatures than polypropylene. Furthermore, nylon has a much higher tenacity and is considerably more extensible than polypropylene. However, polypropylene is considerably lighter than nylon so that the overall weight of the rope may be kept down by using it.

Of course, if desired, the nylon and polypropylene outer yarns of the outer strands may be combined in various other ways to give the desired result. For example, the yarns 20 and 21 need not be alternated 1:1 but can be disposed in a 1:2 or 2:1 or other ratio. Another possibility is to form the yarns 21 with an outer layer of nylon and inner yarns of polypropylene. Still another is to make each or selected ones of the outer yarns of the strands with interspersed nylon and polypropylene components. Of course, any other relatively high melting point plastic material such as a polyester may be used instead of nylon. Similarly, if desired, polyethylene yarns may be used instead of or in combination with the polypropylene yarns, although polyethylenes melting point is even lower than that of polypropylene.

Surrounded by the outer yarns 20 and 21 of the outer strands are a plurality of inner, essentially untwisted, substantially parallel, continuous nylon multi-filaments, for example. These untwisted filaments are fed from spools of such yarns through a compression tube. The 3-ply nylon multi-filaments 21 and the 3-ply polypropylene monofilaments 20 are then applied together with the compressed core filaments through another compression tube to the stranding machine which twists them into the final strand.

The novel rope described herein has been found to have excellent strength characteristics. A rope made according to the teachings herein and having a cross-sectional diameter of about 2.15" successfully replaced a 1% diameter wire rope without the disadvantages of the latter enumerated above. Where not so much strength is necessary, the central rope core can be made primarily of compressed, essentially untwisted nylon or polyester multi-filaments.

Of course, other variations of the present invention, which do not depart from its essence, may occur to one skilled in the art after reading this specification and perusing the drawings herein. Consequently, I desire the invention to be limited solely by the claims herein. Also, the figures herein are purely schematic and the relative dimensions of the rope components are purely for clarity of illustration and are not considered to be limiting in any way.

I claim:

1. A rope comprising:

(a) a central rope core disposed substantially along the longitudinal axis of the rope, said core comprising a plurality of yarns of a synthetic plastic material having a high tensile strength, and

(b) a plurality of strands twisted around said rope core, each of said strands comprising:

(i) an outer layer which includes a first plurality of yarns of a synthetic plastic material having a high tensile strength and also includes a second plurality of yarns of a synthetic plastic material having a lower melting point than said first plurality of yarns,

(ii) a strand core located inwardly of said outer layer (i), said strand core comprising a plurality of substantially untwisted filaments of a synthetic plastic material having a high tensile strength.

2. The rope according to claim 1 wherein there are at least four of said strands twisted around said rope core and wherein said plurality of yarns in said rope core include a plurality of plied yarns.

3. The rope according to claim 2 wherein there are at least six of said strands around said rope core and wherein said plurality of yarns in said rope core consist principally of plied yarns.

4. The rope according to claim 3 wherein each of said strand cores consists primarily of said substantially untwisted synthetic plastic filaments.

5. The rope according to claim 4 wherein said synthetic plastic material of said rope core, said outer layer (i) and said strand core (ii) which has a high tensile strength is from the class of polymers consisting of nylon and polyesters.

6. The rope according to claim 5 wherein said synthetic plastic material in said outer layer having said lower melting point is from the class of polyolefins of propylene and ethylene.

7. A rope comprising:

(a) a central rope core disposed substantially along the longitudinal axis of said rope, said rope core principally comprising a plurality of plied yarns of a synthetic plastic material of a high tensile strength,

(b) six strands surrounding said core, a selected number of said strands comprising, respectively:

(i) an outer layer which includes a plurality of synthetic plastic yarns having a high tensile strength, and

(ii) a strand core disposed inwardly of said outer layer (i) said strand core consisting principally of a plurality of substantially untwisted filaments of a synthetic plastic material having a high tensile strength.

References Cited UNITED STATES PATENTS FRANK J. COHEN, Primary Examiner.

W. H. SCHROEDER, Assistant Examiner.

U.S. Cl. X.R. 

